1. Field of the Invention
The present invention relates to a reflection mirror equipped with a luminance sensor, which is capable of reflecting light from a light source toward an object to be illuminated while measuring the luminance on the object.
2. Description of the Related Art
Reflection mirrors have been used in various apparatus, such as an exposing apparatus used for the manufacture of printed circuit boards.
Such reflection mirrors are made of a bright material such as aluminum alloy. For example, aluminum alloy plate is polished to improve brightness and is then attached to the curved reflection surface of a reflection mirror. Alternatively, an aluminum alloy block is machined to have a curved reflection surface, and the curved reflection surface is plated with chromium in order to improve the brightness. In order to obtain further improved brightness, the curved surface is plated first with nickel and then with chromium. Further, a multi-layer coating is vacuum deposited together with a black heat absorbing layer in order to enable the reflection mirror to sustain overheat stamming from infrared rays.
When the above-described reflection mirror is used to reflect light from a light source toward an object to be illuminated, the luminance on the illuminated surface of the object changes slightly according to the conditions of the reflection surface and the like. Therefore, mere visual check cannot be used to determine whether the object is properly illuminated. Moreover, the object cannot be illuminated properly unless a carefully selected mirror is used.